Furthermore, mutations in genes affecting β-cell development in zebrafish result in phenotypes mimicking those associated with human diseases; for example, PDX1 is linked to genetic forms of diabetes and is associated with increased susceptibility to type 2 diabetes in humans22 and pdx1 mutant fish display key features of diabetes, including hyperglycemia, reduced insulin and reduced β-cell number23. This evidence concerns the gene PDX1 and type 2 diabetes mellitus.